21006259640 has 16 divisors (see below), whose sum is σ = 47264084280. Its totient is φ = 8402503840.

The previous prime is 21006259607. The next prime is 21006259709. The reversal of 21006259640 is 4695260012.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21006259640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 262578206 + ... + 262578285.

Almost surely, 2^21006259640 is an apocalyptic number.

21006259640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21006259640 is an abundant number, since it is smaller than the sum of its proper divisors (26257824640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21006259640 is a wasteful number, since it uses less digits than its factorization.

21006259640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 525156502 (or 525156498 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 35.

The spelling of 21006259640 in words is "twenty-one billion, six million, two hundred fifty-nine thousand, six hundred forty".